I've used one of those Cross Benderz stacked over a Paiste china, to add a bit more "Trash" to the sound. It worked wonderfully. That said, all the various other Factory Metal products that I have tried, have done nothing for me personnally.
Note: don't stack one of these things over an expensive china, because it will scratch the hell out of your cymbal. I was using a Paiste 18" PST-5 China (cheap but still sounded good, just a little gongy, hence the reason I tried this).